Moisture box



May 21, 1940- L. E. DE GIVE 2,201,389

MOISTURE BOX Filed Aug. 2e, 1939 ATTORNE b Y Patented May 21, 1940 UNITED- STATES PATENT OFFICE l,

The invention is a cabinet for curing'or seasoning materials under prescribed constant conditions of surrounding atmosphere,` especially materials which require a high degree of constancy of 'both temperature and humidity, as for example, the test samples incident to the manufacture of' hydraulic cements and the like, the proper treatment of which does not tolerate any substantial variation from a constant condition.

atmosphere within a curing cabinet is automatically kept substantially 4constant as to both temperature and relative humidity over long periods and notwithstanding that the materials or samples themselves may be undergoing chemical changes involving the ltransfer of. both heat and r Heretofore the automatic control of f moisture. such cabinet has been considered exceptionally good if the temperature variation was as little as 3 F., with corresponding changes in relative humidity, but by the system herein disclosed the variation is confined less than'one-half degree and is normally not over 0.4". F., with a corresponding constancy of the relative humidity.

The drawing shows the preferred form of the' on line III- III of Fig. 1,` and Fig. 4 a section'of.

the heater'units. Y The cabinet proper, marked I, is provided with a central vertical partition 2 and a series of interior shelves 3 of Wire-mesh, or other type suited to support the material or test-pieces without too much obstruction to air circulation.- Access is afforded to' the shelves by suitable hinged doors which appear in Fig. 2 and are normally closed. 'I'he cabinet and its doors may be of any suitable construction preferably heat insulated throughout, although perfect insulation is not required. v 'To the bottom of the cabinet proper there is attachedv a supplementary uninsulated metal chamber 4 in communication with the shelf chamber through the openings 5 and 6 at either side, thus providing for an air circulation whichA descends through the opening 5, flows thence,

chamber to separate the water surface from.

evaporative contact with the air ow, but permit i and insulated from it as indicated in Fig. 2.

some heat exchange from one to the other. The rest of the lower chamber is constituted of a shallower and narrower passage I in which the -fan 8 is located and through which the fan draws the air from the wider part thus giving it maximum velocity at this point. All of, the internal surfaces of the two chambers are appropriately sloped to drain any condensed moisture toward v the waterreservoir in the lower chamber. By the apparatus constituting this invention the An electric heater unit Il ismounted in the lower chamber side wall in a horizontalY position This heater is of elongatedform so as to accommodate a wide wick and is formed of an electric resistance coil I3 housed within a very thin walled tube (Fig. 4) with no thick metallic `parts within the chamber such as would serve as reservoirs of heat, and consequently it heats and cools a1- most instantaneously or without lag. The head or base of. this heater, which necessarily contains more metal than the coil and tube, is preferably mounted on the exterior of the chamber wall As shown by the diagram, the current to the motor is branched to the heater unit I I, just described, through a hygrostat switch Il, mounted on the side wall of the cabinet in the ascending sidev of the air circulation, and the heater II is therefore rendered active or inactive onthe call of this hygrostat. 'I'he latter may be of the mercurial r bimetallic type but-is of high sensibility and adapted to control its circuit on a fractional degree change and it is adjustable to workon different selected temperatures. Such yinstru-` ments are available on the market and do not require description. Its bulb'element is covered with a wick that is kept saturated by dipping into a Water cup I5.

' mounted in the ascending air current a dry bulb thermostat I6 connected in another branch of.

.the motor circuit in series with a second electric heater unit Il, constituted o`f a naked resistance coil and located in the passage 'I directly in front l of the circulation fan and therefore at the point of highestA velocity in the circulation.

This thermostat I6 is also of lthe high sensibility type and will be understood to call the lheater I1V into and out of action according to minute variations of the (dry bulb) temperature ofthe ascending air.

For observation purposes two other thermal indicators I8 and I9, either direct or recording. are provided in the cabinet side wall I9 with their bulb elements on the inside of. the cabinet and their scales visible on the outside. One of them, I8, has its bulb kept wetted by means of a wick dipping into a water cup 20 and the bulb of the other is naked, but both are subject to the same air iiow.

'I'he operation is yas follows: Assuming, for example, that it is required to maintain a constant relative humidity of, say, 96.4% at a constant temperature of '70 F., the hygrostat I4 and the thermostat I 6 are set accordingly and the fan circuit is closed starting the circulation. If the initial conditions are less than the settings, one or both of the heater elements at once become active and continue so until the condition corresponding to the settings has been obtained. The heating of the broad band of wicking I2 generates ywater-vapor which is taken up by the air current and further heated by its passage over the heater I6, thereby increasing the temperature and adding moisture. Thereafter variation of either factor of thecondition will call one or the other heater units into or out of action, it being noted that the eect of heater Il is to supply heat plus vapor while the heater l1 lsupplies heat alone and further that the relatively large volume of water in the tank 4 being closely related to the path of air flow functions to oppose or hold back excessive temperature changes, thus contributing to'the uniformity of the condition.

I claim:

l. A seasoning cabinet comprising an upper shelf-containing chamber and a lower chamber with connecting passages between them to accommodate air circulation including both chambers, an air circulating fan in the lower chamber and a constant level water reservoir therein for holding a body of water adjacent to' shelf chamber respectively connected to control the circuits of said heater units.

2. A seasoning cabinet comprising an upper shelf-containing chamber and a lower chamber in communication therewith to accommodate an air circulation including both chambers, said lower chamber having a deep part for holding water and a shallower part, said deep part having v a wick-covered electric heater unit mounted over the water with said wick dipping into said water, said shallower part having an electric heater unit and a fan mounted therein, and hygrostatic and thermostatic control members mounted in the upper chamber and respectively controlling said wick-covered and other heater unit.

3. A seasoning cabinet comprising an upper shelf-containing insulated chamber and a lower chamber in communication therewith for to gether accommodating an air circulation, said lower chamber having a deep part for holding a body offwater and a shallower and narrower part, -an electric fan and an electric heater unit mounted in said narrower part and in the air circulation, a slotted cover over the said body of Water adapted-to separate the air flow therefrom, an elongated electric heater unit horizontally mounted over the cover and provided with a wick dipping in the water through the cover slot, and thermostatic and hygrostatic control members mounted in the shelf chamber, respectively controlling the circuits of said heater units.

4. A seasoning cabinet comprising an upper shelf-containing chamber and a lower chamber with connecting passages between them to accommodate air circulation including both chambers, an air circulating fan in the lower chamberI and a water reservoir therein for holding a relatively large body of water in heatexchanging relation to but out of contact with the air-flow, means for delivering vapor from said water to the air flow, lan electric heater` mounted in the air-now, and a hygrostat and a thermostat in the shelf chamber respectively connected to control said means and heater.

LOUIS P. ne GIVE. 

